void main(){
  var map1={1:'hello','then':'goodbye'};
  print(map1);
  print(map1[1]);
  print(map1['then']);
  map1[1]='hi';
  print(map1);
  map1.remove(1);
  print(map1);

  const map2={1:'dart',2:'javascript'};
  print(map2.keys);
  print(map2.containsKey(1));
  print(map2.values);
  print(map2.containsValue(2));
  map2.forEach((key,value){print('key=$key,value=$value');});

  var map3=new Map();
  print(map3.length);
  print(map3.isNotEmpty);
  print(map3.isEmpty);

  print([1,2,3].asMap());
}
